This invention relates to a fuel supply unit comprising a pump and an electromotor around which the fuel flows. The pump and electromotor are surrounded by a common housing having an inlet channel and an outlet channel, whereby fuel is returned through a return channel from the pressure side to the suction side.
The return channel insures that a certain minimum quantity of fuel flows around the pump and the electromotor if, for example, only a small quantity of fuel is required, as when the vehicle is stopped. In this manner one avoids the formation of gas bubbles in the supplied fuel which would result in a stop of the internal-combustion engine. On the front surface on the pressure side of the housing of so-called inside tank pumps a nozzle is provided from which the quantity of fuel required for cooling flows back into the fuel tank. While this solution is very simple, it can not be applied to outside tank pumps. Until now a return channel of a defined cross-section was provided for outside tank pumps which from the consumption place, for example, from the carburetor of the internal-combustion engine leads back to the fuel tank. This solution is expensive, because in modern vehicles with front engine and fuel tank located above of the rear axle a long return pipe is required which must be corrosion-resistant. Further, the mounting and installation of this return pipe is entailed with difficulties, particularly since a by-pass has to be inserted into the real fuel pipe.